In a device using a battery as a power source, often a DC/DC converter is provided as a power supply circuit for supplying power to a load. The DC/DC converter includes a switching element and an inductor, and by switching the switching element on/off based on a PWM signal, transforms (increases or decreases) voltage from the battery and outputs the transformed voltage to the load. With the DC/DC converter, even if the voltage of the external battery fluctuates, a constant voltage can be applied to the load by transforming (increasing or decreasing) the voltage from the battery.
As control schemes for stabilizing the output voltage of the DC/DC converter, there are known a voltage mode control scheme of feeding back the output voltage, a current mode control scheme of feeding back an output current in addition to the output voltage, and the like.
JP H10-323027A discloses a technique of switching a switching frequency for the switching element according to the output current in order to realize a DC/DC converter capable of suppressing a ripple current and maintaining a high transformation efficiency.
However, in a case of switching the switching frequency as with the DC/DC converter described in JP H10-323027A, there is a problem that the output voltage greatly fluctuates immediately after switching. The output voltage of the DC/DC converter is determined by an average value of inductor current flowing through the inductor, and immediately after switching the switching frequency, the inductor current is larger than the inductor current in the steady state, so the output voltage also increases. As a result, there is a problem that a constant voltage cannot be stably outputted to the load.
The present invention was made in view of the above circumstances, and it is an object of the present invention to provide a voltage conversion device and a voltage conversion method in which even immediately after switching the switching frequency, it is possible to suppress fluctuation of the output voltage, and possible to output a constant voltage to the load in a stable manner.